docs: def _get_billing_cycle_number(self, billing_cycle):
          """Gets the 1-indexed number of the billing cycle relative to the provided billing cycle"""
          begins_before_initial_date = billing_cycle.date_range.lower < self.initial_billing_cycle.date_range.lower
          if begins_before_initial_date:
              raise ProvidedBillingCycleBeginsBeforeInitialBillingCycle(
                  '{} precedes initial cycle {}'.format(billing_cycle, self.initial_billing_cycle)
              )
  
          billing_cycle_number = BillingCycle.objects.filter(
              date_range__contained_by=DateRange(
                  self.initial_billing_cycle.date_range.lower,
                  billing_cycle.date_range.upper,
                  bounds='[]',
              ),
          ).count()
  
          return billing_cycle_number